There are two types of peppermint supplements being sold: mentha pipereta that this study looked at, and mentha arvensis.
I wonder if mentha arvensis has the same effect. Supplements vs mint tea would be another interesting thing to study in future.
Based on your new information, I think it would be good to test the effect of supplemenths vs supplemints.
Based on your new information, I think it would be good to test the effect of supplemenths vs supplemints.